Method of manufacturing flexible fibrous sheet materials



United States Patent "ice U.S. Cl. 260-75 Claims ABSTRACT OF THE DISCLOSURE A method of making flexible fibrous sheet material which comprises forming a fibrous sheet from fibers of a blended polymeric composition without impregnating the sheet with a solution or emulsion of a polymeric material, and dissolving out from the sheet at least one of the polymeric materials constituting the fibers of blended polymeric composition.

This invention relates to a method of manufacturing flexible fibrous sheet materials.

This application is a continuation-in-part of our copending application S.N. 485,527, filed Sept. 7, 1965, now abandoned.

Fibrous sheet materials, particularly unwoven cloths, of natural, artificial, and other fibres have heretofore been limited in their application to fields such as linings, sanitary napkins and felt, and even in these uses they are not deemed adequate in qualities and properties. In order to meet the current demands satisfactorily and also to explore future possibilities, it is believed essential that they should be further improved in their qualities.

Of all the requirements for fibrous sheet materials such as unwoven cloths, bulkiness, that is, largeness of space or volume occupied by the fibrous sheet materials,

is generally contradictory to the strength requirement.

Bulkiness forms the basis of other essential properties of the materials such as waterand air-retaining abilities, air permeability, and moisture permeability, and also has important bearings upon the airiness, touch, and outward appearance of the products. However, it has been inevitable in the prior art but bulkiness has been possible only at the expense of the strength of resulting cloth.

In order to keep sheet materials from losing strength while allowing them to retain as much bulkiness as possible, it has been the practice in the prior art to bond together the single fibres which constitute the sheet materials. However, the sheet materials in which the single fibres are bonded together by prior-art methods have had a serious drawback, that is, loss of flexibility.

The object of the invention is to provide a method of manufacturing very tenacious and bulky and yet flexible sheet materials.

In short, the invention provides a method of making flexible fibrous sheet material which comprises forming a fibrous sheet from fibres of a blended polymeric composition without impregnating the sheet with a solution or emulsion of a polymeric material, and dissolving out from the sheet at least one of the polymeric materials constituting the fibres of blended polymeric composition.

The fibres of blended polymeric composition for use in the invention may be obtained from a mixture of two or more types of polymeric material by Wet spinning, dry spinning, or melt spinning, preferably by the process last mentioned. Also, the yarns are preferably stretched after the spinning.

3,531,439 Patented Sept. 29, 1970 Typical polymeric materials useful in the invention are homopolymers or copolymers including polyolefins such as polyethylene and polypropylene, atactic or isotactic polystyrenes, alkyland halogen-substituted polystyrene, polyamides such as nylon-6 and nylon-66, polyesters such as polyethylene terephthalate, polymethacrylic esters such as polymethyl methacrylate, polyvinyl acetals, acetalized with various aldehydes, polyvinyl alcohols, polyvinyl halides such as polyvinyl chloride, polyacrylonitriles, polyvinylidene halides such as polyvinylidene chloride, copolymers of condensationor polymerization-type monomers, and graft copolymers obtained by grafting the various polymeric materials with various monomers. In selecting the two or more polymers, it is of course necessary to see that they are capable of being spun together. In this connection it must be noted that the capability of mixed spinning means that the compounds when spun into yarns have to maintain the shapes as such, as the yarns so made need not have homogeneously mixed internal structures.

From the composite filaments webs are formed. If the resulting webs are rough and too bulky and if it is desired to obtain highly tenacious end products, the webs are compacted in a suitable way.

A preferred method of compacting consists of cutting the fibre of blended polymeric composition to short staple, treating the short staple on a random webber to form a random web, and then compacting and three-dimensionalizing the random web by needle punching. If the web is not compacted sufliciently by the above procedure, it is further compressed, preferably with application of heat. For compacting purposes, it is also possible to shrink the fibres. Especially in the case where the end product is required to have good tenacity, the sheet materials is preferably subjected to shrinking in lieu of the compacting treatment by needle punching.

The sheet material compacted as above has fair strength, but the bulkiness, or the largeness of internal space or cavity possessed by the sheet material, is lost. As to flexibility, the sheet material is sufficiently compacted and deprived of the bulkiness, and may be said in that sense, to be destitute of flexibility. However, it may also be said to be flexible in that the filaments constituting the sheet material are not bonded to one another. At any rate, even if it lacks flexibility in sufiiciently bulky and flexible by a subsequent step of the manufacturing process.

Following the steps above described, the sheet material is extracted with a solvent for removal of at least one of the polymeric materials constituting the fibres. In the sheet material thus obtained, the constituent filaments themselves possess numerous minute hollow portions.

Thus, the numerous fine cavities in the materials fashioned in accordance with the invention are attributed not merely to the spaces among the constituent filaments but also to the cavities in the filaments themselves. The total sum of the cavities in the filaments constituting a sheet depends on the mixing ratio of the different types of polymeric material. This will be illustrated by an example wherein one kind of polymeric material is extracted from a fibre consisting of two kinds of polymeric material.

Mixed chips prepared by mixing and kneading nylon-6 and polystyrene at diflerent mixing ratios were extruded through nozzles having one hundred 0.2 mm.-dia. orifices each to produce filaments of different mixing ratios. The filaments were then stretched by 300 percent at C. and then by 50 percent at 200 C. (to a total stretching rate of 500 percent). From the products, polystyrene was removed by extraction.

For the purpose of extraction, the products were dipped 3 in benzene at 65 C. repeatedly until the polystyrene content was removed completely. The special hollow filament yarns obtained by the procedure described above had properties as shown in the following table.

Amount of polystyrene in mixture,

4 into a random web. Thereafter, the random web was pressed by a hot roller at 100 C., to a highly tenacious and compact sheet form.

The sheet material thus obtained was dipped in a percent 5 40 50 60 80 Before extraction:

Denier size,d 3.0 3.0 3.0 3.0 3.1 3.0 3.0 Tenacity, g./d 7.3 7.6 7.2 6.5 6.0 5.8 5.2 Elongation, percent 2.1 2.3 1.9 2.3 2.4 2.3 2.2 After extraction:

Denier size, d 2.9 2.9 2.9 2.4 1.0 1.5 1.2 Tenacity, g./d 7.2 7.5 7.0 6.7 6.8 6.5 6.9 Elongation, percent 2.3 2.4 2.5 2.1 2.3 2. 5 2.1 Porosity, percent 3 4 6 20 38 49 60 assistantttastaatazz} M9 w 1 Extraction destroyed the fibrous state of product.

In the above table the porosity indicates values of toluene solution to remove by extraction the polystyrene, C a constituent of the fibre of blended polymers. Then, the (l lOO toluene was washed away with methanol, and methanol 20 was removed by washing the resultant with water. When? These treatments afforded a highly tenacious, bulky, C is denier of the fibre after extraction, and flexlble Sheet matenal' D is denier of a fibre of the insoluble component only EXAMPLE 2 having the same sectional area as that of the former. 95 M d h t f 55 t f l h 1 xe c SCOSlSlIl o arso o t n sheet mammals produced In accordance with the terep hthalate and 1 5 par fs of polv styrene w ere fed ifit gggifigiyfiiggtggi g pg g themselves have an extruder having a 40 mm.-dia. screw, and extruded n th 0 h a noz le havin 100 holes, each 0.25 mm. in d1- It is essential that the solvent for dissolving at least one 5 1 and extrushgm was reeled up at a rate of 500 :5 g m mateilals g fi i l fibres 3 30 meters per minute. The molten polymer stream was cooled p ymenc Compos o t e mYennOn e a so by cold air supplied to said stream through a hood provent for at least one of the polymeric materials (extractvided below said 1 able content) which constitutes the fibre of blended pol- The filaments of blended polymers were cut to Short ymeric material(s) (nonextractable consituents). While staple fibres of 2.5 cm long and the short Staple fib tha type of solvent to be employed FP the type of were extended over a roller dard and mixed up. The stafibre blendfad l f composmon f solvents ple fibres so mixed up were combed, piled up crosswise, useful in the invention include methanol solutions of caland formed by a random wehher into a random cium chloride, titanium tetrachloride, and lithium chlo- Then the web was threehimensionahzed by needle punch. ride, other salt solutions, organic solvents such as cyclic ing compacted by pressing with a hot roller, whereby Z3113; oicrilrcriifohlttisfieaigalhlggfinghdaigorlyigf igz ggg ggl a highly tenacious and compact sheet material was obtaine plhrthrslds, aqueous solutions of various salts, and their m1x- Next, the Sheet material was dipped in benzene at 0 01 t e n the fibre was almost com letel The sheet materials produced in accordance with the i i zg g lgg p y invention are highly tenacious, bulky, and flexible, and The sheet material thus obtained was highly tenacious, are not merely able to dlsplay such excellent properties bulky and flexibh fully in the ordinary uses of sheet materials but also can EXAMPLE 3 expand the applications into fields which have been left unexplored. A mixture of 55 percent of nylon-6 and 45 percent of Typical applications for the sheet materials produced polystyrene were charged into a screw extruder having by the method of the invention are: linings, wall paper, a 40 mm.-dia. to be fused and kneaded together at 300 felt, base cloth for artificial leather, towels, hats and caps, C., and extruded through a nozzle having one hundred handkerchieves, diapers, sheetings, substitute for absorbent 0.25 mm.-dia. holes, and the extruded filament was cotton, pp materials, eyeglass Cleaners, pp iq e reeled up at a velocity of 800 m./min. Prior to the windmaterials, filters, electric insulating materials, building maing eration, the molten polymer stream was cooled by terials, plastics bases, and eye bands. an air flow from a hood provided below the nozzle. The Under the invention, starch or other polymeric material fil t were drawn four-fold at 175 C d h 15. which is not capable of forming fibres alone may be used fold at 210 C., crimped, and cut to obtain staple fibres as the soluble content of the intermediate product. f 2,5 long, Th fibre were separated in water, ex-

The present invention will be further described heret d d over a i gauze t a lap f uniform thickness, under with reference to examples thereof, which are not hi h was th f d i b t en hot roller kept at 100 limitative. C., compressed and compacted to a sheet. The sheet was EXAMPLE 1 dipped in toluene at 90 C. for removal of polystyrene A mixture of 60 parts of nylon-6 and 50 parts of polyi extractloP: Whef1 g s-Permeable, bully andi tenacious styrene was kneaded together, and extruded by a screw 05 S eet matenal t good lusture was 0 tame extruder, through a nozzle having 300 orifices, each 0.2 What We clalm fib h 1 mm. in diameter, at a nozzle temperature of 300 C., A methqd of makfng flexl e mus S eet matena while air was blown through a hood to the drafting por- Whlch compnses formmg a fibrous sheetlfroni Staple tion in the vicinity of the nozzle whereby to cool said draftf' j form from filanjlents of f' P0 i ing portion to 120 C. The extruded filament was wound poslllon the Pf' ,matenals m sald b ended Poly up at a rate of 600 mm per minute merrc composltlon consrstmg of two or more polymers The resulting filaments of blended polymers were cut Selected P rolystyrenesr Polyamldes, 9 to short staple fibres 3 cm. long, extended over a roller estiifs, P y y q f P Y Yl alcohols, P y y card and mixed up. The mixed staple fibres were combed, halldes, polyacfylonltl'lles, 0f Polyvlnyhdene hahdes, piled up crosswise, and then formed by a random webber dissolving out from the sheet at least one of the polymeric materials constituting the staple fibers of blended polymeric composition.

2. A method as claimed in claim 1, wherein the fibrous sheet material is formed as a non-woven random web prior to said dissolving out at least one of said polymeric materials.

3. A method as claimed in claim 2, wherein the web is compacted by a needle-punching process.

4. A method as claimed in claim 2, wherein the web is compacted by compression.

5. A method as claimed in claim 2, wherein the web is compacted by shrinking the fibers.

6. A method as claimed in claim 1, wherein the polymeric materials in the said blended polymeric composition comprise polyamide and polystyrene and the polymeric material which is eventually dissolved out is polystyrene.

7. A method as claimed in claim 1, wherein the polymeric materials in the said blended polymeric composition comprise polyester and polystyrene and the polymeric material which is eventually dissolved out is polystyrene.

8. Flexible fibrous sheet material made by the method as claimed in claim 1.

9. Flexible fibrous sheet material made by the method as claimed in claim 6.

10. Flexible fibrous sheet material made by the method as claimed in claim 7.

References Cited UNITED STATES PATENTS 3,375,209 3/1968 Kemper 260-2.5 2,940,871 8/1955 Johannsen 260--2.5 3,367,891 11/1968 Ingram 2602.5 2,268,160 3/1944 Miles 260-2.5 2,409,704 10/1946 Lyem 156-307 X 2,380,003 7/1945 Whitehead 156-307 X 2,773,286 12/1956 Piccard 2602.5 3,053,609 9/1962 Miller 156305 X 3,375,208 3/1968 Daddy 2602.5

CARL D. QUARFORTH, Primary Examiner 20 G. SOLYST, Assistant Examiner US. Cl. X.R. 

